The present invention relates to a method of gathering the ends of heat-conducting pipes in a heat exchanger without use of end plates.
In the conventional practice of gathering the ends of heat-conducting pipes in a heat exchanger, many holes are bored in end plates; the ends of heat-conducting pipes are fitted into the holes; and ends of the pipes are welded to the end plates. In welding of the pipe ends to the end plates, however, the thermal strain due to thermal expansion in the longitudinal direction of the heat-conducting pipes cannot be absorbed, and in the worst case the end plates are broken owing to the thermal strain in the pipes. Meanwhile welding execution makes it impossible to narrow the interval between adjacent holes in the end plate, and accordingly the heat exchanger cannot be made compact in configuration. When welding is executed with the interval between adjacent holes unreasonably narrowed, the thermal strain in the adjacent pipes cannot be absorbed, resulting in failure of the pipes or in cracking of the end plate.
Impossibility of narrowing the interval between holes in the end plate means impossibility of narrowing the gap between adjacent pipes. Therefore, the flow of the fluid passing through the space formed around adjacent pipes is retarded and in consequence a laminar flow develops around the pipes, impeding heat transfer between the fluid in the heat-conducting pipes and the fluid passing through the gaps between adjacent pipes, with the result that the efficiency of heat transfer drops.